Refrigerating apparatus



w A. o. G'ROOMS 2,129,373

REFRIGERATING APPARATUS Original Filed March 19, 1 9-34 Patented Sept.6, 1938 UNITED STATES PATENT OFFICE-l eral Motors Corporation ration ofDelaware Dayton, Ohio, a corpo- Application March i9, 1934, Serial No.716,305 Renewed April-24, 1936 17 Claims, (Cl. 62-4) This inventionrelates to refrigerating apparatus and more particularly to controlmeans therefor.

Ordinarily the evaporator of a mechanical refrigerating system isoperated at freezing temperatures. This causes frost to collect upon theevaporator which retards the cooling action of the evaporator and lowersthe thermal efliciency of the system. It has been proposed to defrostthe evaporator periodically by employing a ratchet device operated bythe opening or closing of the temperature controlling switch toperiodically raise the evaporator temperature for defrosting.

I have found that at least in some situations,

particularly where a small switch mechanism is used and where lowevaporator temperatures with a rathersmall dilierential are required,that such a defrosting arrangement places a greater load upon the switchoperatingmechanism than can properly be performed thereby and thisreduces the sensitiveness of the switch operation. It is therefore anobject of my invention to provide a means for. periodically varying thetemperature of the evaporating means which does not place an additionalload upon the switch operating mechanism or effect the sensitivity ofthe switch mechanism.

It is another object of my invention to compensate the defrosting meansfor changes in the temperature regulating mechanism of the switch meansso that substantially the same defrosting temperatures are obtainedregardless of the setting of the temperature mechanism, and to providemeans for rendering the defrosting means ineffective.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein a preferred form of the present invention is clearlyshown.

In the drawing:

Fig. 1 is a diagrammatic view of a refrigerating system together with asectional view of a control means embodying my invention; and- Fig. 2 isa fragmentary view showing a modified form of my invention.

Referring to the drawing there is shown a, compressor '20 forcompressing the refrigerant and for forwarding the compressedrefrigerant to a condenser 2| where the compressed refrigerantisliquefied and collected in a receiver 22. From the receiver 22 theliquid refrigerant is forwarded through a supply conduit 23-to anevaporator or cooling unit 24 shown as of the flooded low side floatcontrolled type. This evaporator 24 is located within the foodcompartment 25 of a refrigerator cabinet 26. The evaporator 24 cools theair within the food compartment 25 and also freezes water in the icetray 21 in order to make ice cubes. In cooling the food compart-' mentand freezing ice cubes, the liquid refriger- 5 ant within the evaporator24 evaporates and is returned to the compressor through the returnconduit 28. The compressor 20 is driven by an electric motor 29 which issupplied with electric energy through an electric circuit 30 which is 10under the control of my improved control means 3|.

The control means 3| is operated by a metal bellows 32 connected bytubing 33 to the return conduit 28 so that it is responsive to thepressure 1 and therefore the temperature of the flooded low side floattype of evaporator 24. The bellows 32 operates the main switch lever 34pivoted at 35 to the casing 36 of the control means. The main switchlever 34 is connected to a toggle type of'20 snap acting mechanism 3'!through which opens and closes the set of switch contacts 38 located inthe electric motor circuit 30. The expansion of the bellows 32 isopposed bya compression type coil spring 39 which so controls the move25 ment of the main switch lever 34 as to cause the switch contacts 38to be opened and closed in order to maintain proper refrigeratingtemperatures within the evaporator 24. In order to vary the temperaturesof the evaporating means 24, 30 I provide a temperature regulating screw40 which through a follower 4| controls the tension of the temperatureregulating spring 39. By varying the tension of the temperatureregulating spring 33, the temperatures at which the 35 switch contacts38 are opened and closed may be controlled.

In order to maintain proper temperatures within the food compartment 25and to freeze any water in the ice tray 21 it is ordinarily neces- 40sary to maintain an evaporator 24 at freezing temperatures. This causesfrost to collect and accumulate upon the surfaces of the evaporator 24by the condensation and freezing of' moisture I from the air upon itssurfaces. This retards the 45 cooling effect of the evaporator 24 andlowers the thermal efliciency of .the system since this frost acts as asort of an insulator.

It has been proposed to provide a ratchet device controlled and operatedby the opening and clos- 50 ing of the switch mechanism for periodicallyinterposing additional resistance to the expansion of the switchoperating bellows in order to cause the evaporator to attain atemperature above freezing so that the frost will melt from the sur- 55faces of the evaporator. I have found, however, that this affects thesensitivity of the switch, particularly when the switch is small indimension, since the control and operation of the ratchet device placesan additional load or resistance upon the bellows which operates theswitch mechanism. This affects the sensitivity of the switch since theoperation of such a ratchet device increases the frictional load uponthe bellows and also places an additional load which is not alwaysuniform and therefore cannot well be compensated for. This objectionablefeature be comes more objectionable when low pressures and lowtemperatures are required, particularly with a rather smalldifferential.

In order to avoid this objectionable situation, in my device I do notdepend upon the switch mechanism for controlling or operating theratchet device but, on the other hand, I use an external source ofpower. As one structural embodiment for using an external source ofpower for controlling defrosting, I have provided a bimetal strip 58which is anchored at one end of a block 5| extending from the casing 35.The opposite or free end of the bimetal strip is adapted to engage theteeth 52 of a ratchet wheel 53 which is rotatably mounted upon a pin 54fixed to a vertically slidable rod 55 which slides within a guidingaperture in a boss 55; This rod is provided with a pawl 51 whichcooperates with the teeth 52 of the ratchet wheel 53 and bimetal strip50 in order to insure rotation of the ratchet wheel 53 in the properdirection.

The rod 55 is urged in a downward direction by the compression type coilspring 58 which at its upper end rests against a spring retainer 58carried at the lower end of a defrosting mechanism regulating screw 58which is threaded through a lever 5|. The lever 6| is pivoted at its midpoint upon a pivot pin 82 and at its opposite end is provided with aforked end portion 53 which is received within a groove 54 formed in thelower portion of the temperature regulating screw 48. This causes thetension of the spring 58 to be adjusted through the lever 5| by anyadjustment of the temperature regulating screw 48 so as to compensatefor the changes caused by the adjustment of the screw 48.

The ratchet wheel 53 is provided with a pin or arm 55 which is rivetedthereto and which projects therefrom radially so as to cooperate withthe projection 58 formed upon the main switch lever ll whenever the arm85 is in the position shown in Fig. 1. When the arm 85 is in thisposition and the bellows 32 expands during the off cycle this expansionof the bellows 32 will be resisted by the tension of the spring 39 aswell as the tension of the defrosting spring 58. This will necessitatethat the evaporator 24 attain a higher temperature than normal,preferably several degrees above freezing before sufilcient pressure isobtained within the bellows 32 in order to overcome the tension of thesprings 88 and 58 in order to close the switch contacts 88 and theelectric circuit 30 in order to permit the motor 28 to start therefrigerating system.

When the electric circuit 38 is closed, electric current flows throughthe heater 61 which is in series with the electric circuit 38 and theswitch contacts 28 and in close proximity to the bimetal strip 58. Thecurrent flowing through the heater 81 causes it to become heated and toheat the bimetal strip 50 thereby causing the free end of the blmetalstrip 58 to curl upwardly and by its engagement with one of the teeth 52of the ratchet wheel 53 will rotate the ratchet wheel in acounterclockwise direction for the distance of about one tooth. Thiswill cause the arm 55 to move out of the path of the projection 58 uponthe main switch lever 34 and permit the switch mechanism and therefrigerating system to again resume normal operation. The rod 55 isprovided with a pin 58 which limits its downward movement.

When it is desired to freeze water within the ice tray 21, it is usuallyundesirable to permit the evaporator to be defrosted. I thereforeprovide means for rendering the defrosting means inoperative. This isprovided by a finger manipulator 18 pivoted to the casing by a pin H.This finger manipulator 18 has an effective and an ineffective positionwhich are determined by a leaf spring 12. The finger manipulator 18 isconnected by a rod 13 and a lost motion connection to an extension 14and extending from the rod 55. This lost motion connection is providedby extending the rod 13 through an aperture in the extension l4 andproviding a nut and lock nut 15 upon the lower end of the rod 13. Theconnection between the finger manipulator l8 and the rod '13 are soproportioned that when the finger manipulator"!!! is thrown to effectiveposition to render the defrosting mechanism inoperative, the rod 13 ispulled upwardly to engage the extension 14 so that the arm 65 of thedefrosting mechanism is prevented from engaging the projection 66 uponthe switch lever 34, and at the same time the connection between the rod13 and the finger manipulator 18 is thrown across the dead centerposition. By throwing the finger manipulator 18 from the dead centerposition, it is resiliently held in this position by the tension of thespring 58 until it is again returned manually to ineffective position;

By my mechanism I have relieved the bellows 32 from operating theratchet device and used a bimetal strip and heater connected with theelectric circuit supplied with electric energy from an external sourcein order to perform this operation. By this mechanism the ratchet wheel53 is stepped around approximately one tooth every time the switch isclosed so that the number of cycles and the number of teeth upon theratchet wheel govern the frequency of the defrosting period.

In Fig. 2, I have shown a fragmentary view which illustrates a modifiedarrangement wherein the compressor motor having an electric circuit 8|controlled by the opening and closing of the switch contacts 82 isprovided with a high resistance electric heater 83 in parallel with theswitch contacts 82 so that this heater has electric energy flowingthrough it only when the switch contacts 82 are open. This causes thebimetal strip 84 to be heated during the off cycle of the refrigeratingsystem and this, of course, causes the ratchet wheel 53 to be moved in acounterclockwise direction during the off cycles of the refrigeratingsystem instead of during the on cycles of the system as illustrated inthe form shown in Fig. 1. This circuit arrangement eliminates thenecessity of the entire motor current from passing through the heater ofthe bimetal strip.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

fecting by physical force the operation of the controlling means toperiodically cause the tempera-, ture of the evaporating means to bechanged from normal.

2. Refrigerating apparatus including refrigerant liquefying means andrefrigerant evaporating means, means for cyclically controlling theliquefying means to normally maintain the evaporating means at a normalaverage temperature, means for conducting electric energy to saidliquefying means, and thermal means heated by electric energy flowingthrough said conducting means for periodically affecting by physicalforce the operation of said controlling means to periodicallycause thetemperature of the evaporating means to be changed from normal.

3. Refrigerating apparatus including refrigerant liquefying means andrefrigerant evaporating means, means for cyclically controlling theliquefying means to normally maintain the evaporating means at anormalaverage temperature, a bimetal powered ratcheting means for affecting byphysical force the operation of the cyclically controlling means tocause the temperature of the evaporating means to mal.

4. Refrigerating apparatus including refrigerant liquefying' means andrefrigerant evaporating means, means for conducting electric energy tosaid liquefying means, means for cyclically controlling the supplyofelectric energy to said liquefying means to normally maintain theevaporating means at a normal average temperature, a bimetal poweredratcheting device energized by the electric energy flowing through saidconducting means for periodically causing the tem-J perature of theevaporating means to be changed from normal. r

5. Refrigerating apparatus including refrigerant liquefying means andrefrigerant evaporating means, means for cyclically controlling theliquefyingmeans to normally maintain the evaporating means at a normalaverage temperature, and a bimetal powered ratcheting device forperiodically interposing a resistance to the operation of thecontrolling means to periodically cause the temperature of theevaporating means to be changed from normal.

6. Refrigerating apparatus including refrigerant liquefying means andrefrigerant evaporating means, means for 'cyclically controlling theliquefying means to normally maintain the evaporating means at a normalaverage temperature, a ratcheting device provided with means forperiodically mechanically affecting the normal operation of the controlof the liquefying means means mechanically independent of the cyclicalcontrol means but responsive to the cycling of the liquefying means forratcheting the ratcheting device.

7. Refrigerating apparatus including refriger ant liquefying means, andrefrigerant evaporating means/means for cyclically controlling theliquefying means to normally maintain the evaporating means at a normalaverage temperature, a

ratcheting device provided with means for p ebe changed fromnorriodically mechanically affecting the normal operation of the controlof the liquefying means to periodically cause the temperature of theevaporating means to be changed from normal, and electrical meansenergized once each cycle of the liquefying means for ratcheting theratcheting device.

8. Refrigerating apparatus including a cooling unit adapted to containa" refrigerant medium, means for circulating the refrigerant mediumthrough said cooling unit, means for cyclicallyv controlling thecirculation of the refrigerant medium to normallymaintain the coolingunit at a normal average temperature, means powered mechanicallyindependently of the cyclical control means but responsive to the cyclesof circulation of the refrigerant medium for periodically mechanicallyafiectingthe normal action of the cyclical control means to periodicallycause the temperature of the evaporating means to be changed fromnormal, and means operable at will for rendering said independentlypowered means ineffective to change the temperature of the cooling unitfrom normal.

9. Refrigerating apparatus including refrigerant liquefying means andrefrigerantevaporating-means, means for cyclically controlling theliquefying means to normally maintain the evaporating means at a normalaverage temperature, means for adjusting said cyclically controlledmeans to vary said normal average temperature, means poweredmechanically independently of the cyclically controlled means forperiodically affecting the control of the liquefying means toperiodically cause the temperature of the evaporating means to bechanged from normal, and means responsive to the movement of saidadjusting means for varying the effect of said independently poweredmeans. I

10. Refrigerating apparatus including a cooling unit, means forcirculating a refrigerant medium through the unit, control meansresponsive to the temperature of the cooling unit for. controlling thestarting and stopping of the circulation of the refrigerant mediumthrough the unit, means for controlling the action of the control meansto provide a-normal relationship between the temperature of the coolingunit and the .starting 'of the circulation, a cycle counting devicepowered mechanically independently of said control means forperiodically changing the control of the action'of the control means toperiodically change the relationship between the temperature of thecooling unit and the starting of the circulation.

11. Refrigeratingapparatus including a cooling unit, means forcirculating a refrigerant medium through the cooling unit, control meansfor start-.

ing and stopping the circulation of refrigerant medium at definite highand low cooling unit temperature limits, a cycle counting devicepowmeans for normally maintaining said evaporat ing means at freezingtemperatures, and a bimetal operated device for periodically disturbingthe control of one of said means to permit the temfreezing temperatures.

13. Refrigerating apparatus including refrigerperature of theevaporating means to rise above ant liquefying means and refrigerantevaporating means, a control means for one of said means for normallymaintaining said evaporating means at freezing temperatures, and abimetal operated ratcheting device for periodically disturbing thecontrol of one of said means to permit the temperature of theevaporating means to rise above freezing temperatures.

\ 14. Refrigerating apparatus including refrigerant liquefying means andrefrigerant evaporating means, a control means for one of said means fornormally maintaining said evaporating means at freezing temperatures,and an electrically heated bimetal operated device for periodicallydisturbing the control of one of said means to permit the temperature ofthe evaporating means to rise above freezing temperatures.

15. Refrigerating apparatus including electrically operated refrigerantliquefying means and refrigerant evaporating means, means for conductingelectric energy to said liquefying means, means for cyclicallycontrolling the supply of en-- ergy to said liquefying means to maintainsaid evaporating means at a normal average temperature, and meansoperated by the heating effect of electrical energy supplied by saidconducting means for periodically disturbing the control of one of saidmeans to vary the normal average temperature of the evaporating means.

16. Refrigerating apparatus including electrically operated refrigerantliquefying means and refrigerant evaporating means, means for conductingelectric energy to said liquefying means, means for cyclicallycontrolling the supply of energy to said liquefying means to maintainsaid evaporatingmeans at a normal average temperature, and a ratchetingdevice having thermal operating means operated by the heating effect ofelectrical energy supplied by said conducting means for periodicallydisturbing the control of one of said means to vary the normal averagetemperature of the evaporating means.

1'7. Refrigerating apparatus including refrigerant liquefying means andrefrigerant evaporating means, cyclical control means for cyclicallycontrolling the liquefying means to normally maintain the evaporatingmeans at a normal average temperature, and mechanically independentlypowered means responsive to the cycling of the liquefying means forperiodically mechanically affecting the operation of the cyclicalcontrol means to periodically cause the temperature of the evaporatingmeans to be changed from normal, said mechanically independently poweredmeans being powered mechanically independently of the cyclical controlmeans.

ALBERT O. GROOMS.

